Carbocycloxyalkyl cephalosporins



United States Patent 3,222,363 CARBOCYCLOXYALKYL CEPHALOSPORINS Edwin H. Flynn, Indianapolis, Ind., assignor to Eli Lilly and Company, Indianapolis, Ind., a corporation of Indiana No Drawing. Filed Aug. 23, 1961, Ser. No. 133,339 3 Claims. (Cl. 260243) This invention relates to novel organic compounds and to methods for their preparation.

The novel compounds of this invention are represented by the following structural formula:

LR: ll

in which R taken alone, is OH, C -C acyloxy, or tertiaryamino, R is OH when R is OH, R is OH when R is C -C acyloxy, R is O* when R is tertiary-amino, R and R when taken together, are 0--, and R is represented by the following formula:

* R 0-R -d in which R is C C, alkylene, either straight or branchedchain; and R is benzyl, naphthyl, naphthylmethyl, C -C cycloalkyl, C -C cycloalkylmethyl, or substitution prod- A ucts thereof.

Thus, R can be acetoxy, propionoxy, butyroxy, capryloxy, .or the like; or N-pyridyl, N-pyrimidyl, trimethylamino, triethylamino, tributylamino, or other tertiary-amino group such as those produced by reaction of cephalosporin C with nicotine, nicotinic acid, isonicotinic acid, nicotinamide, 2-aminopyridine, 2-amino-6- methylpyridine, 2,4,6 trimethylpyridine, 2 hydroxyinethylpyridine, sulfapyridine, 3-hydroxypyridine, pyridine-2,3-dicarboxylic acid, quinoline, sulfadiazine, sulfa'thiazole, picolinic acid, and the like.

R can be methyl, a straight-chain alkylene radical having two to four carbon atoms, or a branched alkylene radical having three or four carbon atoms; and R can be attached at any of the carbon atoms having a replaceable hydrogen atom. Thus, R can have the skeletal configuration of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl, with R substituted for a hydrogen atom thereon.

R can be benzyl, a-naphthyl, a-naphthylmethyl, finaphthyl, 13- naphthylmethyl, cyclobutyl, cyclobutylmethyl, cyclopentyl, cyclopentylmethyl, cyclohexyl, or cyclohexylmethyl, or substitution products thereof, having in each case one 01; more chlorine, bromine, fluorine, iodine, nitro, trifiuordmethyl, C -C alkyl, or C -C alkoxy substituents upon the ring.

The novel compounds of the present invention are related to cephalosporin C insofar as they contain the 5,6-dihydro-2H-1,3-thiazine ring with a fused B-lactam ring in the 2,3 position which is characteristic of cephalosporin C. However, unlike cephalosporin C, which contains the -amino-N-adipamyl group in the 7 position, the compounds of the present invention are characterized by an acylamido group in the 7 position having attached thereto a carbocyclic radical through an ether linkage. Moreover, unlike cephalosporin C, which has a relatively low antibacterial action, the compounds of the present invention are highly effective antibacterial agents, capable of inhibiting the growth of numerous types of microorganisms in a variety of environments. 1

3,222,363 Patented Dec. 7,, 1965 As will be observed from the formulas given above, the invention includes a variety of related compounds having the bicyclic ring structure of cephalosporin C, but with variations in the substituent groups attached thereto. Among such compounds are those having the nuclei of the cephalosporin-type products known as cephalosporin C desacetylcephalosporin C, and cephalosporin C these nuclei being represented by the following formulas, respectively:

where Am represents a tertiary-amino radical, exemplified above. As will be seen from the above formulas, the nucleus of cephalosporin C includes a fused lactone ring, while the nucleus of cephalosporin C forms an inner salt or zwitteriou. I

As is the case with the penicillins, to which the compounds of this invention are in some degree related, numerous salts, esters, amides, and like derivatives thereof can be prepared by combination with nontoxic pharmaceutically acceptable cations, anions, alcohol residues, ammonia, and amines, and such derivatives are to be regarded as the full equivalents of the compounds disclosed and claimed herein, and accordingly are to be considered as within the scope of this invention.

For purpose of illustration, there can be mentioned several types of cationic salts which can be prepared from compounds containing the cephalosporin C nucleus, including, for example, water-soluble salts such as the sodium, potassium, lithium, ammonium, and substituted ammonium salts, as well as the less water-soluble salts such as the calcium, barium, procaine, qinine, and dibenzylethylenediamine salts. Those compounds which contain "the cephalosporin C nucleus do not form cationic salts but instead form anionic salts, i.e., acid addition salts, with strong acids such as hydrochloric, hydrobromic, phosphoric, sulfuric, and like acids.

The following examples, together with the operating examples appearing hereinafter, will illustrate the types of compounds available in accordance with the present invention:

7-,8-benzyloxya,a-dimethylpropionarnidocephalosporanic acid 7-02-0chlorobenzyloxy-a-methyl-n-butyramidocephalosporanic acid 7 aa-naphthoxy) isovaleramidocephalosporanic acid 7-aa'-naphthylmethoxy) n-butyramidocephalosporanic acid 7-m-(,8-naphthylmethoxy)isobutyramidocephalosporanic acid 7- -cyclobutoxy-n-butyramidocephalosporanic acid 7-fi- 2-fluorocyclobutylmethoxy propionamidocephalosporanic acid 7-6-(3'-methylcyclopentoxy)n-valeramidocephalosporanic acid 7-a-cyclopentylmethoxypropionamidocephalosporanic acid 7-'y-cyclohexoxy-u-methyl-n-butyramidocephalosporanic acid 7-oc-cyclohexylmethoxy-n-butyramidocephalosporanic acid 7-o-nitrobenzyloxyacetamidocephalosporanic acid 7-ot-m-trifluoromethylbenzyloxypropionamidocephalo- 'sporanic acid 7-o-1nethoxybenzyloxyacetamidocephalosporanic acid 7-[3-p-ethoxybenzyloxyisobutyramidocephalosporanic acid and the like, including the cephalosporin C A and cephalosporin C analogues thereof.

Cephalosporin C can be prepared by cultivating. a cephalosporin C-producing organism in a suitable nutrient medium, as described in British patent specification 810,- 196, published March 11, 1959.

Cephalosporin C is readily converted into cephalosporin C by heating with water under acid conditions, as described in Belgian Patent 593,777, published November 30, 1960. This removes the acetyl group from its point of attachment through oxygen to the methyl group in the position of the thiazine ring, and lactonization then spontaneously occurs, yielding the fused cyclic lactone.

Cephalosporin C is also readily converted into compounds of the cephalosporin C type by refluxing in aqueous solution with an excess of pyridine, for example, as described in Belgian Patent 593,777. The reaction is applicable in general to the tertiary amines, of which numerous examples are given above, yielding corresponding derivatives of the cephalosporin C type wherein the tertiary amine is attached to the methyl group in the 5 position of the thiazine ring, and forms an inner salt with the carboxyl group in the 4 position.

Desacetylcephalosporin C is conveniently prepared by treating cephalosporin C with citrus acetylesterase for several hours in aqueous phosphate buffer at pH 6.5-7 according to the method of Jansen, lang, and MacDonnell, Archiv. Biochem., (1947), 415-431.

From the various cephalosporin C compounds thus available, the corresponding nucleus is readily obtained by cleaving the 5'-amino-N'-adipamyl side chain between its amido nitrogen and its amido carbonyl group. Thus, 7-aminocephalosporanic acid can be obtained by digesting cephalosporin C for an extended period in the presence of a mineral acid and in the absence of light, according to the method described in Belgian Patent 593,777.

The compounds of the present invention are prepared by acylation of the appropriate cephalosporin C nucleus, be it the nucleus of cephalosporin C itself or of cephalosporin C or cephalosporin C or other variant. Alternatively, compounds of the cephalosporin C C and desacetylcephalosporin C classess can be obtained by applying to appropriate 7-acylamidocephalosporanic acids the conversion procedures of Belgian Patent 593,777 and of Jansen et al. to produce compounds having the respective nuclei.

For the acylation of the 7-amino group of the cephalosporin nucleus, as defined above, any of the conventional acylation procedures can be employed, utilizing any of the various types of known acylating agents having a composition which yields the desired side chain.

A convenient acylating agent is the appropriate carbocyclic ether-linked acyl chloride or bromide. The acylation is carried out in water or an appropriate organic solin about 20 percent excess, with stirring and cooling. The pH of the mixture can be maintained, if it tends to vary, around the neutral level by bubbling carbon dioxide therein. After addition of the acylating agent has been completed, stirring of the reaction mixture is continued, and the mixture is allowed to warm to room temperature. The reaction product is then acidified to around pH 2 and extracted with an organic solvent such as ethyl acetate. The ethyl acetate extract is adjusted to around pH 5.5 with a base containing the desired cation of the final product, and is extracted with water. The water solution is separated and evaporated to dryness. The residue is taken up in the minimum quantity of water, and the desired product is precipitated by adding a large excess of acetone and, if necessary, ether. The crystalline product obtained thereby is filtered, washed with acetone, and dried.

Acylation can also be carried out with the corresponding carbocyclic ether-linked alkylenyl carboxylic acid, employed in conjunction with an equimolar proportion of a carbodiimide such as N,N'-diisopropylcarbodiimide, N, N'-dicyelohexylcarbodiimide, N,N'-bis(p-dirnethylaminophenyl) carb odiimide, N-ethyl-N'- (4"-ethylm-orpholinyl carbodiimide, or the like, and the acylation proceeds at ordinary temperatures in such cases.

Alternatively, the carbocyclic ether-linked alkylenyl carboxylic acid can be converted into the corresponding acid anhydride, or into the azide, or into an activated ester, and any of these derivatives can be used to efiect the desired acylation. Other agents can readily be ascertained from the art.

In many cases, the acylating agent may contain one or more asymmetric carbon atoms and thus exist in optically active forms. When prepared by ordinary chemical means, such compounds are ordinarily obtained in racemic formi.e., an equimolar mixture of the optical isomers, having no optical rotation. When the separate optical isomers are desired, the acylating agent can be resolved in a conventional manner such as by reacting the free acid with cinchonine, strychnine, brucine, or the like, then fractionally crystallizing to separate the diestereoisomeric salts, and separately acidifying the solid phase and the liquid phase to liberate the optical isomers. The free acids thus obtained can be employed as such for the acylation, preferably in conjunction with a carbodiimide, or may be converted by conventional means into the corresponding acid halide or into a mixed anhydride, care being exercised to avoid extremes of conditions which might produce racemization.

Many of the acylating agents, together with methods for their preparation, are described in the literature, and a number of them are commercially available. All of them are readily prepared by methods well known in the art.

The invention will be more readily understood from the following operating examples, which are submitted as illustrations only, and not by way of limitation. The chemical assays reported herein were carried out by the method of Ford, Analytical Chemistry, 19, 1004 (1947), which is based upon the quantitative determination of the ,B-lactam moiety of the cephalosporin molecule via reaction with hydroxylamine. The antibiotic potencies were deter mined against (Staphylococcus aureus 209-P by an appropriate modification of the paper disc plate methods of Higgens et al., Antibiotics & Chemotherapy, 3, 50-54 (January 1953), and Loo et al., Journal of Bacteriology, 50, 701709 (1945). The pKa values were determined by titration in aqueous 66 percent dimethylformamide.

EXAMPLE 1 7-BenzyIoxyacetamidocephalosporanic acid One gram of 7-a-minocephalosporanic acid was suspended in 50 ml. of water, and 1.0 g. of sodium bicarbonate was added. After solution was complete, 50 ml. of acetone were added, and the solution was stirred and cooled in an ice bath. To the cold solution was added a solution of 683 mg. of benzyloxyacetyl chloride in 15 ml. of acetone over a period of one hour at 5 C., and stirring was continued thereafter for one hour. The acetone was stripped off under vacuum. To the residual aqueous solution were added 75 ml. of ethyl acetate, and the mixture was adjusted to pH 2 with 1 N hydrochloric acid. Thelayers were separated, and the ethyl acetate layer was back-extracted at pH 5.5 with 75 ml. of water, pH adjustment being effected with aqueous 1 N potassium hydroxide solution. The aqueous extract was stripped under vacuum to a semisolid. The latter was dissolved in acetone, stripped, dissolved in hot methanol, diluted with isopropyl alcohol to the point of turbidity, and stripped to a solid. The yield was 960 mg. of 7-benzyloxyacetamidocephalosporanic acid in the form of the potassium salt, having a pKa of 15.0 and a maximum in its ultraviolet absorption spectrum at 260 m (e=6,880). The product had a chemical assay of 1340 penicillin G units per milligram.

EXAMPLE 2 7-fi-naphthoxyacetamidocephalosporanic acid 7-aminocephalosporanic acid (1.0 g.) was suspended in a mixture of 50 ml. of water and 50 ml. of acetone, and sodium bicarbonate (1.2 g.) was added. When solution was essentially complete, 50 ml. of acetone were added, and the solution was cooled to 5 C. in an ice bath. To the cold solution was then added with stirring a solution of 820 mg. of fI-naphthoxyacetyl chloride in 15 m1. of acetone over a period of one hour, after which stirring was continued for two hours while the mixture warmed to room temperature. The acetone was then stripped off under vacuum, and the residual aqueous solution was adjusted to pH 3.9 with aqueous 1 N potassium hydroxide solution and washed with 50 ml. of benzene. The washed aqueous solution was layered with 100 ml. of ethyl acetate and adjusted to pH 2.1 with 1 N hydrochloric acid. The layers were separated. The ethyl acetate layer was back-extracted into 60 ml. of water at pH 5.4, aqueous 1 N potassium hydroxide solution being used for the pH adjustment. The aqueous extract was evaporated under vacuum to a syrup. The syrup was solidified by dilution with acetone, and the amorphous solid produced thereby was filtered off. The solid, weighing 1.58 g., was purified by triturating with 10 ml. of Warm methanol, cooling, filtering, washing with methanol, and drying. The yield was 1.30 g. of

7 3 naphthoxyacetamidocephalosporanic acid in the form of the potassium salt, having a pKa of 4.90 and maxima in its ultraviolet absorption spectrum at 228 and 340 m (e:33,150 and 3,500, respectively), with a shoulder at 306 mg. The product had a chemical assay of 1450 penicillin G units per milligram and an antibiotic potency of 51 penicillin G units per milligram.

I claim:

1. 7-benzyloxyacetamidocephalosporanic acid.

2. 7-/8-naphthoxyacetamidocephalosporanic acid.

3. An antibiotic substance of the class represented by the following formula:

References Cited by the Examiner UNITED STATES PATENTS 6/1960 Doyle et al. 260239.1

FOREIGN PATENTS 593,777 12/1960 Belgium.

OTHER REFERENCES Burger: Medicinal Chemistry, page 46 (1960). WertheimzTextbook of Organic Chemistry, pp. 763- 764 (1945).

NICHOLAS S. RIZZO, Pnimary Examiner. 

3. AN ANTIBIOTIC SUBSTANCE OF THE CLASS REPRESENTED BY THE FOLLOWING FORMULA: 